What Causes Frequent Spotting?

Hello, I m currently in transit and unable to visit a doctor at the moment (will soon though) but I am experiencing spotting. I have sex very infrequently with my fiance, however our last time was two months ago. Since then I ve had two periods, but started spotting about a week ago, right in the middle of my cycle (continuously for the past week). I took a pregnancy test anyway, and the test came back negative. Can I be pregnant still despite a negative test two months later and two periods? Or what might be the issue? Thanks so much!